The present invention relates generally to a multi-system laser safety shutter controller.
In the modern laboratory environment, the laser has become commonplace. From materials research and testing to communications and optical computing, lasers have proven to be valuable tools for research. Along with this usefulness, lasers pose an inherent safety hazard. One immediately thinks of burns as the primary hazard of laser operation; however, this is not the case. A more important concern is the ability of laser light to blind an unsuspecting individual. Surprisingly low intensity levels of laser radiation can cause permanent vision loss before the human eye can react. For this reason, vision safety should be of paramount importance in a laser environment.
The foremost method of vision protection from laser radiation is the use of safety goggles. Goggles with filters for blocking laser light at various wavelengths are available from a multitude of manufacturers. If chosen and worn properly, they provide adequate protection to those working with lasers while still allowing adequate visual perception to perform normal laboratory functions.
While safety goggles provide protection to announced visitors or those individuals who regularly work with lasers, the unexpected guest is still at extreme risk. To provide protection to these individuals, most lasers incorporate an interlock mechanism that shuts the laser down during an unexpected breach of the laser work area. Usually, a switch of some sort is connected to the entrance doors of the laboratory that activates the interlock. However, while this type of mechanism is extremely useful in a secure laboratory, it may not be well suited for a more "heavily travelled" lab. This is because most interlock mechanisms operate by shutting down the laser power supply. Doing this requires that the laser be restarted after each shutdown. This situation is very inconvenient and may be damaging to the laser. An alternative to this system is a safety shutter.
A safety shutter functions by blocking the laser beam when a laboratory intrusion occurs. This is more convenient than the interlock mechanism, and it produces no strain on the laser system. The safety shutter can be controlled the same as an interlock, and it provides a convenient means of stopping the laser beam when the rearrangement of an experiment is required.
The following United States patents relate to various safety devices for lasers.
U.S. Pat. No. 4,856,874--Tusting
U.S. Pat. No. 4,730,113--Edwards et al
U.S. Pat. No. 4,663,520--Tanaka et al
U.S. Pat. No. 4,415,231--Kaczensky et al
The Tusting patent describes a safety device for submarine lasers. The laser is enclosed in a water-proof housing with a window portion. The laser device emits coherent light through the window only when the laser device is immersed in water. Shutter means prevents coherent light from being emitted through the window unless the laser device is immersed in water. The shutter means can be activated by a pressure switch, shutter float, or some similar device. The Edwards et al patent relates to a safety system for a laser-utility facility. The system comprises a safety enclosure and an infra-red monitoring system. The monitoring system detects hot spots at internal surfaces of the enclosure walls. Detection of a hot spot leads to shutting of the laser source or interrupting the laser beam by means of a shutter. The Tanaka et al patent describes a fail-safe laser apparatus in which a laser beam radiation source emits a laser beam along an optical axis. The apparatus comprises a main shutter, a safety shutter, a first and second sensor, and a detection circuit. The first sensor produces a first signal indicative of the intensity of the laser beam between the source and the main shutter, and the second sensor produces a second signal which is indicative of the intensity of the laser beam between the main shutter and the safety shutter. A detection circuit is responsive to any excessive laser beam energy indicated by the sensor signals, and manipulates the safety shutter accordingly. The Kaczensky et al patent relates to a radiation shutter which prevents laser radiation from exiting the source. Two filter and/or diaphragm systems are individually switchable into the radiation path in series fashion. Each system has an actuator for positioning the respective radiation stopping system in response to a control signal provided by a sensor of the respective previous system.